Rotational rheometer

Abstract

A rotational rheometer has an integrating motor (1), which rotates a measuring shaft (16) supporting a first measuring element (4), there being formed between this first measuring element (4) and a further, fixed measuring element (5) a measurement gap (S), into which is introduced the substance to be tested (12), in particular fluid, the depth of the measurement gap (S) being variable by the adjustment of the two measuring elements (4, 5) relative to each other, and a device being provided to determine the distance between the two measuring elements. At least one inductive or at least one magnetic position sensor (19, 21) is supported by one of the two measuring elements (4, 5). The first measuring element (4) or a device (18) disposed on this measuring element (4) can cause the position sensor (19, 21) disposed on the other measuring element (5) to respond, or can cause the output signal, e.g. impedance, resistance,or voltage, of this position sensor (19, 21) to be modified, and the output signals of the position sensor (19, 21) are supplied to an analyzing unit (22, 24, 17).

What is claimed is:  
     
       1. A rotational rheometer with an integrating motor, which rotates a measuring shaft supporting a first measuring element, there being formed between this first measuring element and a second, fixed measuring element, a measurement gap, into which is introduced the substance to be tested, the depth of the measurement gap being variable by the adjustment of the first and second measuring elements relative to each other, and a device being provided to determine a mutual distance between the first and second measuring elements, wherein 
       in order to establish or measure, and/or set, and/or keep constant the depth of the measurement gap in a non-contact manner, at least one inductive or at least one magnetic position sensor generates output signals and is supported by one of the first and second measuring elements;  
       the first measuring element causes the position sensor disposed on the second measuring element to respond in dependence upon the distance between the first and second measuring elements or causes an output signal of the at least one position sensor to be modified; and  
       the output signals of the at least one position sensor are supplied to an analyzing unit.  
     
     
       2. A rotational rheometer according to  claim 1 , wherein the position sensor supported by the second measuring element comprises an inductive position sensor having at least one solenoid supported by the second measuring element or embedded in the second measuring element, 
       the first measuring element supporting a component made of magnetically soft material, or the first measuring element being made of magnetically soft material at least in a region facing the solenoid, and  
       the impedance values of the at least one solenoid being supplied to the analyzing unit as output signals of the inductive position sensor.  
     
     
       3. A rotational rheometer according to  claim 2 , wherein the at least one solenoid carries one of alternating current and alternating voltage. 
     
     
       4. A rotational rheometer according to  claim 2 , wherein the at least one solenoid comprises a solenoid core. 
     
     
       5. A rotational rheometer according to  claim 2 , wherein the at least one solenoid is partly embedded in the second measuring element. 
     
     
       6. A rotational rheometer according to  claim 2 , wherein the component or the first measuring element being made of magnetically soft material faces the solenoid in its entirety. 
     
     
       7. A rotational rheometer according to  claim 1 , wherein the position sensor supported by the second measuring element comprises an inductive position sensor with at least one solenoid supported by the second measuring element or embedded in this measuring element, 
       the first measuring element supporting at least one component made of electrically conductive, nonmagnetic material, or the first measuring element being made of electrically conductive, nonmagnetic material at least in a region facing the solenoid, and  
       the impedance values of the at least one solenoid being supplied to the analyzing unit as output signals of the inductive position sensor.  
     
     
       8. A rotational rheometer according to  claim 7 , wherein the second measuring element is made from material which is nonmagnetic and a poor conductor of electricity, and wherein the solenoid supported by the second measuring element is formed without a core. 
     
     
       9. A rotational rheometer according to  claim 7 , wherein the impedance values of the at least one solenoid can be modified by eddy-current losses. 
     
     
       10. A rotational rheometer according to  claim 1 , wherein the position sensor supported by the second measuring element is a component which responds to magnetic fields; 
       a permanent magnet is supported by the first measuring element or is embedded in the first measuring element, an axis of the permanent magnet preferably being aligned perpendicularly to a face of the position-sensor or to a surface of the second measuring element supporting the magnetic position sensor; and  
       characteristics of the component which can be influenced by magnetic fields are supplied to the analyzing unit.  
     
     
       11. A rotational rheometer according to  claim 10 , wherein the component is one of a Hall-effect sensor and a magnetoresistor. 
     
     
       12. A rotational rheometer according to  claim 10 , wherein the characteristics of the component which can be influenced by magnetic fields comprises one of voltage values and resistance values. 
     
     
       13. A rotational rheometer according to  claim 1 , wherein, for the purpose of measuring the temperature of at least one of the position sensors, the measuring elements, and their surrounding areas, there is provided a temperature sensor associated with the position sensor, output signals of the temperature sensor being supplied to the analyzing unit for temperature compensation of the output signals of the position sensor. 
     
     
       14. A rotational rheometer according to  claim 13 , wherein the temperature sensor is supported by one of the measuring elements. 
     
     
       15. A rotational rheometer according to  claim 1 , wherein the first and second measuring elements are disposed one above the other, and the position sensor is disposed on a lower one of the measuring elements. 
     
     
       16. A rotational rheometer according to  claim 15 , wherein the lower one of the measuring elements is of a size equal to or larger than another one of the measuring elements. 
     
     
       17. A rotational rheometer according to  claim 1 , wherein, for the purpose of setting the distance between the first and second measuring elements, there are provided devices for moving the measuring elements relative to each other, said devices being formed by at least one of linear drives, spindle drives, and Uhing nut drives. 
     
     
       18. A rotational rheometer according to  claim 1 , wherein the second measuring element comprises at least one solenoid set in or on a U-shaped or E-shaped core made of soft iron, transformer sheet, or ferrite. 
     
     
       19. A rotational rheometer according to  claim 1 , wherein the second measuring element comprises at least one solenoid or a component which responds to magnetic fields, and wherein, in order to calculate or establish the impedance of the solenoid, or the voltage, or resistance value of a component, a computer is operatively coupled to the analyzing unit. 
     
     
       20. A rotational rheometer according to  claim 19 , wherein the computer is adapted to adjust the calculated or established impedance of the solenoid as a function of temperature values determined by a temperature sensor. 
     
     
       21. A rotational rheometer according to  claim 1 , wherein the analyzing unit generates further signals in dependence upon the output signals of the position sensor for controlling a device for modifying the measurement gap by adjusting the height at least of one of the first and second measuring elements. 
     
     
       22. A rotational rheometer according to  claim 1 , wherein the first measuring element comprises a member disposed on the second measuring element.